Au@Pt dendrimer encapsulated nanoparticles as model electrocatalysts for comparison of experiment and theory

Abstract

In this paper we report the electrochemical synthesis of core@shell dendrimer-encapsulated nanoparticles (DENs) consisting of cores containing 147 Au atoms (Au 147 ) and Pt shells having $54 or $102 atoms (Au 147 @Pt n (n ¼ 54 or 102)). The significance of this work arises from the correlation of the experimentally determined structural and electrocatalytic properties of these particles with density functional theory (DFT) calculations. Specifically, we describe an experimental and theoretical study of Pb underpotential deposition (UPD) on Au 147 DENs, the structure of both Au 147 @Pb n and Au 147 @Pt n DENs, and the activity of these DENs for the oxygen reduction reaction (ORR). DFT calculations show that Pb binding is stronger on the (100) facets of Au as compared to (111), and the calculated deposition and stripping potentials are consistent with those measured experimentally. Galvanic exchange is used to replace the surface Pb atoms with Pt, and a surface distortion is found for Au 147 @Pt n particles using molecular dynamics simulations in which the Pt-covered (100) facets shear into (111) diamond structures. DFT calculations of oxygen binding show that the distorted surfaces are the most active for the ORR, and that their activity is similar regardless of the Pt coverage. These calculations are consistent with rotating ring-disk voltammetry measurements.

Correlating Structure and Function of Metal Nanoparticles for Catalysis

“…and (111) facets [15]. DFT calculations indicate that Pb UPD oc-232 curs on the (100) facet before the (111) facet.…”

“…[8] 57 Fig. 1 illustrates the synthetic routes to form random alloy [9,7,58 10-12], core-shell [13][14][15][16], and alloy-core@shell DENs [17]. Random 59 alloy DENs are prepared by a co-complexation method, where two 60 types of metal cations are reduced simultaneously to form an alloy par-61 ticle.…”

A theoretical and experimental examination of systematic ligand-induced disorder in Au dendrimer-encapsulated nanoparticles

“…28 Briey, a 250 mL solution of aqueous 2.0 mM Au 147 DENs was synthesized by adding 147 equivalents of HAuCl 4 to a stirred solution of 2.0 mM G6-NH 2 . Au 3+ was allowed to associate with the interior of the dendrimer for 10 min, and then a 10-fold excess of 1.0 M NaBH 4 in 0.30 M NaOH was added to reduce this precursor to Au 147 DENs.…”

From Galvanic to Anti‐Galvanic Synthesis of Bimetallic Nanoparticles and Applications in Catalysis, Sensing, and Materials Science

“…[73] Recent results from our group showed that the GR of click dendrimer-encapsulated CuNPs with Ag + and Au 3+ yielded dendrimer-stabilized noble-metal NPs for which the catalytic reactivity in Cu-catalyzed alkyne azide cycloaddition (CuAAC) and 4-nitrophenol reduction was strongly dependent on the location of the NP in the dendrimer. [76] Very recently this research group has designed the synthesis, using GR, of polyamidoamine (PAMAM) dendrimer-encapsulated trimetallic Pd@Pt-Au nanowires, as efficient electrocatalysts for the ORR. [75] They also carried out GR of Au 147 @Pb n to replace surface Pb atoms with Pt, and density functional theory (DFT) calculations showed that oxygen-binding-involved distortions were most productive for the ORR.…”